Thin film transistor and thin film transistor array panel including the same

ABSTRACT

A thin film transistor according to an exemplary embodiment of the present invention includes an oxide semiconductor. A source electrode and a drain electrode face each other. The source electrode and the drain electrode are positioned at two opposite sides, respectively, of the oxide semiconductor. A low conductive region is positioned between the source electrode or the drain electrode and the oxide semiconductor. An insulating layer is positioned on the oxide semiconductor and the low conductive region. A gate electrode is positioned on the insulating layer. The insulating layer covers the oxide semiconductor and the low conductive region. A carrier concentration of the low conductive region is lower than a carrier concentration of the source electrode or the drain electrode.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. application Ser.No. 14/184,361, filed on Feb. 19, 2014, which is a continuation-in-partof U.S. application Ser. No. 13/553,418, filed on Jul. 19, 2012, issuedas U.S. Pat. No. 8,664,654 on Mar. 4, 2014, which claims priority toKorean Patent Application No. 10-2012-0034099 filed in the KoreanIntellectual Property Office on Apr. 2, 2012, and thecontinuation-in-part application claims priority to Korean PatentApplication No. 10-2012-0034099 filed in the Korean IntellectualProperty Office on Apr. 2, 2012 and Korean Patent Application No.10-2013-0131410 filed in the Korean Intellectual Property Office on Oct.31, 2013, the disclosures of which are incorporated by reference hereinin their entireties.

TECHNICAL FIELD

Embodiments of the present invention relate to a thin film transistor, athin film transistor array panel including the same, and a method ofmanufacturing the same.

DISCUSSION OF THE RELATED ART

Thin film transistors (TFTs) are used in various electronic devices,such as flat panel displays. For example, thin film transistors are usedas switching elements or driving elements in a flat panel display, suchas a liquid crystal display (LCD), an organic light emitting diode(OLED) display, and an electrophoretic display. A thin film transistorincludes a gate electrode connected to a gate line to transmit ascanning signal, a source electrode connected to a data line to transmita signal applied to a pixel electrode, a drain electrode that faces thesource electrode, and a semiconductor electrically connected to thesource electrode and the drain electrode. The semiconductor is a factorin determining characteristics of the thin film transistor. Thesemiconductor may include silicon (Si). The silicon may be amorphoussilicon or polysilicon according to a crystallization type thereof.Amorphous silicon allows for a simpler manufacturing process and hasrelatively low charge mobility. Polysilicon, which has relatively highcharge mobility, is subjected to a crystallizing process, such thatmanufacturing cost is increased and the process is complicated. Toaddress the properties of amorphous silicon and polysilicon, there isresearch on thin film transistors using an oxide semiconductor havinghigh uniformity. The oxide semiconductor can have higher electronmobility, a higher ON/OFF ratio, and a lower cost than those ofamorphous silicon and/or polysilicon. If parasitic capacitance isgenerated between the gate electrode and the source electrode or thedrain electrode of a thin film transistor, characteristics of the thinfilm transistor as a switching element may be deteriorated.

SUMMARY

A thin film transistor according to an exemplary embodiment of thepresent invention includes an oxide semiconductor. A source electrodeand a drain electrode face each other. The source electrode and thedrain electrode are positioned at two opposite sides, respectively, ofthe oxide semiconductor. A low conductive region is positioned betweenthe source electrode or the drain electrode and the oxide semiconductor.An insulating layer is positioned on the oxide semiconductor and the lowconductive region. A gate electrode is positioned on the insulatinglayer. The insulating layer covers the oxide semiconductor and the lowconductive region. A carrier concentration of the low conductive regionis lower than a carrier concentration of the source electrode or thedrain electrode.

A thin film transistor array panel according to an exemplary embodimentof the present invention includes an insulation substrate. An oxidesemiconductor is positioned on the insulation substrate. A sourceelectrode and a drain electrode face each other. The source electrodeand the drain electrode are positioned at two opposite sides,respectively, of the oxide semiconductor. A low conductive region ispositioned between the source electrode or the drain electrode and theoxide semiconductor. An insulating layer is positioned on the oxidesemiconductor and the low conductive region. A gate electrode ispositioned on the insulating layer. The insulating layer covers theoxide semiconductor and the low conductive region. A carrierconcentration of the low conductive region is lower than a carrierconcentration of the source electrode or the drain electrode.

The source electrode and the drain electrode may include a materialreduced from a material of the oxide semiconductor.

An edge boundary of the gate electrode may be positioned inside an edgeboundary of the insulating layer.

The carrier concentration of the low conducive region may be graduallyvaried in the low conductive region.

The edge boundary of the insulating layer may be substantially alignedto a boundary between the low conductive region and the source electrodeor the drain electrode.

The edge boundary of the gate electrode may be substantially aligned toan edge boundary of the oxide semiconductor.

A buffer layer positioned between the insulation substrate and the oxidesemiconductor may be further included.

At least one of the buffer layer or the insulating layer may include aninsulating oxide.

A method of manufacturing a thin film transistor array panel accordingto an exemplary embodiment of the present invention includes forming asemiconductor pattern. The semiconductor pattern includes an oxidesemiconductor material. An insulating layer and a gate electrode areformed. The insulating layer and the gate electrode cross and overlap acenter portion of the semiconductor pattern. The semiconductor patternthat is not covered by the insulating layer and the gate electrode isreduced, forming a semiconductor, a low conductive region, and a sourceelectrode and a drain electrode facing each other with respect to thesemiconductor. The low conductive region is positioned between thesemiconductor and the source electrode or the drain electrode. Theinsulating layer covers the oxide semiconductor and the low conductiveregion. A carrier concentration of the low conductive region is lowerthan a carrier concentration of the source electrode or the drainelectrode.

In the method, an insulating material layer is formed on thesemiconductor pattern. A gate layer is formed on the insulating materiallayer. The gate layer includes a conductive material. A photosensitivefilm pattern is formed on the gate layer. The gate layer is patterned byusing the photosensitive film pattern as an etching mask, forming thegate electrode. The insulating material layer is patterned by using thephotosensitive film pattern as an etching mask, forming the insulatinglayer and expose a portion of the semiconductor pattern.

In the method, a semiconductor layer including an oxide semiconductormaterial, an insulating material layer including an insulating material,and a gate layer including a conductive material are sequentiallyformed. A first photosensitive film pattern is formed on the gate layer.The first photosensitive film pattern includes portions respectivelyhaving different thicknesses from each other. The gate layer, theinsulating material layer, and the semiconductor layer are sequentiallyetched by using the first photosensitive film pattern, forming thesemiconductor pattern. A portion of the first photosensitive filmpattern is removed, forming a second photosensitive film pattern. Thegate layer is patterned by using the second photosensitive film patternas an etching mask, forming the gate electrode. The insulating materiallayer is patterned by using the second photosensitive film pattern as anetching mask, forming the insulating layer and expose a portion of thesemiconductor pattern.

An edge boundary of the gate electrode may be positioned inside an edgeboundary of the insulating layer.

The carrier concentration of the low conductive region may be graduallyvaried in the low conductive region.

A metal component of the oxide semiconductor material may be extractedto a surface of at least one of the source electrode, the drainelectrode, or the low conductive region.

The semiconductor, the low conductive region, the source electrode, andthe drain electrode may be formed using a reduction treatment methodusing plasma.

According to an exemplary embodiment of the present invention, a thinfilm transistor includes a source electrode, a drain electrode, a gateelectrode, and a semiconductor layer. The source electrode and the drainelectrode are disposed on a substrate. The source electrode and thedrain electrode are spaced apart from each other. The semiconductorlayer is disposed on the substrate between the source electrode and thedrain electrode. A low conductive layer is disposed on the substratebetween the source electrode or the drain electrode and thesemiconductor layer. An insulating layer is disposed on thesemiconductor layer and the low conductive layer. The gate electrode isdisposed on the insulating layer. A carrier concentration of the lowconductive layer decreases from the drain or source electrode to thesemiconductor layer.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the present disclosure and many of theattendant aspects thereof will be readily obtained as the same becomesbetter understood by reference to the following detailed descriptionwhen considered in connection with the accompanying drawings, wherein:

FIG. 1A is a cross-sectional view illustrating a thin film transistorarray panel including a thin film transistor according to an exemplaryembodiment of the present invention;

FIG. 1B is a plan view of the thin film transistor array panel of FIG.1A;

FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, FIG. 7, FIG. 8, FIG. 9, and FIG.10 are cross-sectional views sequentially showing a method ofmanufacturing the thin film transistor array panel shown in FIG. 1according to an exemplary embodiment of the present invention;

FIG. 11 is a cross-sectional view illustrating a thin film transistorarray panel including a thin film transistor according to an exemplaryembodiment of the present invention;

FIG. 12, FIG. 13, FIG. 14, FIG. 15, FIG. 16, FIG. 17, FIG. 18, FIG. 19,and FIG. 20 are cross-sectional views sequentially showing a method ofmanufacturing the thin film transistor array panel shown in FIG. 11according to an exemplary embodiment of the present invention;

FIG. 21 is a graph illustrating a voltage-current characteristic of athin film transistor according to an exemplary embodiment of the presentinvention;

FIG. 22 is a graph illustrating a voltage-current characteristicaccording to various source-drain voltages of a thin film transistoraccording to an exemplary embodiment of the present invention;

FIG. 23A is a cross-sectional view illustrating a thin film transistorarray panel including a thin film transistor according to an exemplaryembodiment of the present invention;

FIG. 23B is a plan view of the thin film transistor array panel of FIG.23A;

FIG. 24 to FIG. 33 are views sequentially showing a manufacturing methodof the thin film transistor array panel shown in FIG. 23 according to anexemplary embodiment of the present invention;

FIG. 34 to FIG. 37 are photos showing a cross-section of a thin filmtransistor panel including a thin film transistor according to anexemplary embodiment of the present invention;

FIG. 38 is an enlarged view of the thin film transistor shown in FIG.37;

FIG. 39 and FIG. 40 are graphs showing on-current characteristicsaccording to a gate voltage of a thin film transistor according to anexemplary embodiment of the present invention;

FIG. 41 is a cross-sectional view of a thin film transistor array panelincluding a thin film transistor according to an exemplary embodiment ofthe present invention; and

FIG. 42 to FIG. 49 are views sequentially showing a manufacturing methodof the thin film transistor array panel shown in FIG. 41 according to anexemplary embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

The embodiments of the present invention will be hereinafter describedin greater detail with reference to the accompanying drawings. As thoseskilled in the art would realize, the described embodiments may bemodified in various different ways, all without departing from thespirit or scope of the present invention. Like reference numerals maydesignate like or similar elements throughout the specification and thedrawings. It will be understood that when an element such as a layer,film, region, or substrate is referred to as being “on”, “connected to”,or “coupled to” another element, it can be directly on, connected orcoupled to the other element or intervening elements may also bepresent. As used herein, the singular forms, “a”, “an”, and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise.

FIG. 1A is a cross-sectional view illustrating a thin film transistorarray panel including a thin film transistor according to an exemplaryembodiment of the present invention, and FIG. 1B is a plan view of thethin film transistor array panel of FIG. 1A. Referring to FIG. 1A, alight blocking film 70 is positioned on an insulation substrate 110 madeof glass or plastic. The light blocking film 70 prevents or inhibitslight from reaching an oxide semiconductor included in a channel regionto thereby prevent the oxide semiconductor from losing itscharacteristics. According to an embodiment, the light blocking film 70is made of a material that does not transmit light of a predeterminedwavelength band so that light does not reach the oxide semiconductor.According to an embodiment, the light blocking film 70 is made of anorganic insulating material, an inorganic insulating material, or aconductive material, such as a metal, and according to an embodiment,includes a single layer or multiple layers. According to an embodiment,the light blocking film 70 is omitted. For example, when there is nolight radiation from under the insulation substrate 110, for example,when the thin film transistor according to an exemplary embodiment ofthe present invention is used for an organic light emitting device, thelight blocking film 70 is omitted. A buffer layer 120 is positioned onthe light blocking film 70. According to an embodiment, the buffer layer120 includes an insulating oxide, such as silicon oxide (SiOx), aluminumoxide (Al₂O₃), hafnium oxide (HfO₃), and yttrium oxide (Y₂O₃). Thebuffer layer 120 prevents an impurity from the insulation substrate 110from flowing into a semiconductor to be deposited later, protecting thesemiconductor and improving interface characteristics of thesemiconductor. A thickness of the buffer layer 120 is in a range of morethan about 500 μm to less than about 1 μm, but is not limited thereto. Asemiconductor layer including a channel region 134, a source region 133,and a drain region 135 is formed on the buffer layer 120. Thesemiconductor layer includes an oxide semiconductor material. The oxidesemiconductor material includes a metal oxide semiconductor made of ametal oxide of zinc (Zn), indium (In), gallium (Ga), tin (Sn), ortitanium (Ti), or a combination of the metal of zinc (Zn), indium (In),gallium (Ga), tin (Sn), titanium (Ti), and the metal oxide thereof. Forexample, according to an embodiment, the oxide semiconductor materialincludes at least one of zinc oxide (ZnO), zinc-tin oxide (ZTO),zinc-indium oxide (ZIO), indium oxide (InO), titanium oxide (TiO),indium-gallium-zinc oxide (IGZO), and indium-zinc-tin oxide (IZTO). Thechannel region 134 overlaps the light blocking film 70. Referring toFIGS. 1A and 1B, the source region 133 and the drain region 135 arerespectively positioned at two sides of the channel region 134 and areseparated from each other. The source region 133 and the drain region135 are connected to the channel region 134. The source region 133 andthe drain region 135 have conductivity and include a semiconductormaterial forming the channel region 134 and a reduced semiconductormaterial of the channel region 134. A metal, such as indium (In),included in the semiconductor material may be extracted to a surface ofat least one of the source region 133 and the drain region 135. Aninsulating layer 142 is positioned on the channel region 134. Theinsulating layer 142 covers the channel region 134. The insulating layer142 does not overlap or substantially does not overlap the source region133 or the drain region 135. According to an embodiment, the insulatinglayer 142 includes a single-layered structure or a multilayeredstructure having at least two layers. When the insulating layer 142includes a single-layered structure, the insulating layer 142 includesan insulating oxide, such as silicon oxide (SiOx), aluminum oxide(Al₂O₃), hafnium oxide (HfO₃), and yttrium oxide (Y₂O₃). The insulatinglayer 142 improves interface characteristics of the channel region 134and prevents an impurity from penetrating into the channel region 134.When the insulating layer 142 includes a multilayered structure, theinsulating layer 142 includes a lower layer 142 a and an upper layer 142b as shown in FIG. 1A. The lower layer 142 a includes an insulatingoxide, such as silicon oxide (SiOx), aluminum oxide (Al₂O₃), hafniumoxide (HfO₃), and yttrium oxide (Y₂O₃), such that the interfacecharacteristic of the channel region 134 may be improved and thepenetration of the impurity into the channel region 134 may beprevented. According to an embodiment, the upper layer 142 b is made ofvarious insulating materials, such as silicon nitride (SiNx) and siliconoxide (SiOx). For example, according to an embodiment, the insulatinglayer 142 includes a lower layer of aluminum oxide (AlOx), which has,but is not limited to, a thickness of less than about 500 Å, and anupper layer of silicon oxide (SiOx), which has, but is not limited to, athickness of more than about 500 Å to less than about 1500 Å.Alternatively, the insulating layer 142 includes a lower layer ofsilicon oxide (SiOx), which has, but is not limited to, a thickness ofabout 2000 Å, and an upper layer of silicon nitride (SiNx), which has,but is not limited to, a thickness of about 1000 Å. According to anembodiment, a thickness of the insulating layer 142 is more than 1000 Åto less than 5000 Å, but is not limited thereto. An entire thickness ofthe insulating layer 142 is controlled to maximize the characteristicsof the thin film transistor. A gate electrode 154 is positioned on theinsulating layer 142. An edge of the gate electrode 154 and an edge ofthe insulating layer 142 are aligned or substantially aligned with eachother. Referring to FIGS. 1A and 1B, the gate electrode 154 includes aportion overlapping the channel region 134, and the channel region 134is covered by the gate electrode 154. The source region 133 and thedrain region 135 are positioned at two sides of the channel region 134with respect to the gate electrode 154, and the source region 133 andthe drain region 135 do not overlap or do not substantially overlap thegate electrode 154. Accordingly, the parasitic capacitance between thegate electrode 154 and the source region 133 or the parasiticcapacitance between the gate electrode 154 and the drain region 135 maybe decreased. According to an embodiment, the gate electrode 154 is madeof a metal, such as aluminum (Al), silver (Ag), copper (Cu), molybdenum(Mo), chromium (Cr), tantalum (Ta), and titanium (Ti), or alloysthereof. The gate electrode 154 has a single-layered or multilayeredstructure. According to an embodiment, the multilayered structureincludes a double-layered structure including a lower layer of titanium(Ti), tantalum (Ta), molybdenum (Mo), or ITO and an upper layer ofcopper (Cu). According to an embodiment, when the gate electrodeincludes a multilayered structure, the gate electrode includes atriple-layered structure of molybdenum (Mo)-aluminum (Al)-molybdenum(Mo). According to an embodiment, the gate electrode 154 is made ofvarious metals or conductors. According to an exemplary embodiment ofthe present invention, a boundary between the channel region 134 and thesource region 133 or a boundary between the channel region 134 and thedrain region 135 are aligned or substantially aligned with an edge ofthe gate electrode 154 or the insulating layer 142. Alternatively, theboundary between the channel region 134 and the source region 133 or thedrain region 135 is positioned more inwardly with respect to the edge ofthe gate electrode 154 or the insulating layer 142. The gate electrode154, the source region 133, and the drain region 135 form a thin filmtransistor (TFT) Q along with the channel region 134, and a channel ofthe thin film transistor is formed in the channel region 134. Apassivation layer 160 is positioned on the gate electrode 154, thesource region 133, the drain region 135, and the buffer layer 120.According to an embodiment, the passivation layer 160 is made of aninorganic insulating material, such as silicon nitride or silicon oxide,or an organic insulating material. The passivation layer 160 has acontact hole 163 exposing the source region 133 and a contact hole 165exposing the drain region 135. A data input electrode 173 and a dataoutput electrode 175 are positioned on the passivation layer 160. Thedata input electrode 173 is also referred to as a source electrode, andthe data output electrode 175 is also referred to as a drain electrode

The data input electrode 173 is electrically connected to the sourceregion 133 of the thin film transistor Q through the contact hole 163 ofthe passivation layer 160, and the data output electrode 175 iselectrically connected to the drain region 135 of the thin filmtransistor Q through the contact hole 165 of the passivation layer 160.Alternatively, a color filter (not shown) or an organic layer (notshown) made of an organic material is further positioned on thepassivation layer 160, and the data input electrode 173 and the dataoutput electrode 175 are positioned on the color filter or organiclayer. Alternatively, at least one of the data input electrode 173 andthe data output electrode 175 is omitted. A method of manufacturing thethin film transistor array panel shown in FIG. 1 according to anexemplary embodiment of the present invention is described withreference to FIG. 2 to FIG. 9 as well as FIG. 1. FIG. 2, FIG. 3, FIG. 4,FIG. 5, FIG. 6, FIG. 7, FIG. 8, FIG. 9, and FIG. 10 are cross-sectionalviews sequentially showing a method of manufacturing the thin filmtransistor array panel shown in FIG. 1 according to an exemplaryembodiment of the present invention. Referring to FIG. 2, the lightblocking film 70 made of an organic insulating material, an inorganicinsulating material, or a conductive material, such as a metal, isformed on the insulation substrate 110 made of glass or plastic.According to an embodiment, the forming of the light blocking film 70 isomitted according to the condition. Referring to FIG. 3, the bufferlayer 120 made of an insulating material including an oxide, such assilicon oxide (SiOx), aluminum oxide (Al₂O₃), hafnium oxide (HfO₃), andyttrium oxide (Y₂O₃), is formed on the light blocking film 70 by achemical vapor deposition (CVD) method. A thickness of the buffer layer120 is in a range more than about 500 μm to less than about 1 μm, but isnot limited thereto. Referring to FIG. 4, a semiconductor material layer130 made of an oxide semiconductor material, such as zinc oxide (ZnO),zinc-tin oxide (ZTO), zinc-indium oxide (ZIO), indium oxide (InO),titanium oxide (TiO), indium-gallium-zinc oxide (IGZO), andindium-zinc-tin oxide (IZTO), is coated on the buffer layer 120. Aphotosensitive film including a photoresist is coated on thesemiconductor material layer 130 and is exposed to light, resulting in aphotosensitive film pattern 50. The photosensitive film pattern 50overlaps at least a portion of the light blocking film 70. Referring toFIG. 5, the semiconductor material layer 130 is etched by using thephotosensitive film pattern 50 as a mask to form a semiconductor pattern132. An insulating material layer 140 is formed on the semiconductorpattern 132 and the buffer layer 120. The insulating material layer 140includes a single-layered structure including an insulating oxide ofsilicon oxide (SiOx), or as shown in FIG. 5, includes a multilayeredstructure including a lower layer 140 a including an insulating oxide,such as silicon oxide (SiOx), and an upper layer 140 b including aninsulating material. A thickness of the insulating material layer 140 ismore than about 1000 Å to less than about 5000 Å, but is not limitedthereto. Referring to FIG. 6, a conductive material, such as a metal, isdeposited on the insulating material layer 140 and is patterned to formthe gate electrode 154. The gate electrode 154 is formed to traverse acenter portion of the semiconductor pattern 132 such that two portionsof the semiconductor pattern 132 respectively positioned at two sides ofthe overlapping portion of the gate electrode 154 and the semiconductorpattern 132 are not covered by the gate electrode 154. Referring to FIG.7, the insulating material layer 140 is patterned by using the gateelectrode 154 as an etching mask to form the insulating layer 142.According to an embodiment, the insulating layer 142 includes asingle-layered structure or a multilayered structure that includes alower layer 142 a including an insulating oxide and an upper layer 142 bincluding an insulating material. Accordingly, the gate electrode 154and the insulating layer 142 have the same or substantially the sameplane shape. The two portions of the semiconductor pattern 132 that arenot covered by the gate electrode 154 are exposed. According to anembodiment, the method of patterning the insulating material layer 140includes a dry etching method in which etching gas and etching time arecontrolled for the buffer layer 120 to not be etched. Referring to FIG.8, the two exposed portions of the semiconductor pattern 132 aresubjected to a reduction treatment method, thereby forming the sourceregion 133 and the drain region 135 having conductivity. Thesemiconductor pattern 132 that is covered by the insulating layer 142and is not reduced becomes a channel region 134. Accordingly, the gateelectrode 154, the source region 133, and the drain region 135 form thethin film transistor Q along with the channel region 134. According toan embodiment, the reduction treatment method includes a heat treatmentmethod that is performed in a reduction atmosphere and a gas plasmatreatment using plasma, such as hydrogen (H₂), helium (He), phosphine(PH₃), ammonia (NH₃), silane (SiH₄), methane (CH₄), acetylene (C₂H₂),diborane (B₂H₆), carbon dioxide (CO₂), germane (GeH₄), hydrogen selenide(H₂Se), hydrogen sulfide (H₂S), argon (Ar), nitrogen (N₂), nitrogenoxide (N₂O), and fluoroform (CHF₃). At least a portion of thesemiconductor material forming the reduced and exposed semiconductorpattern 132 has only metallic bonding. Accordingly, the reducedsemiconductor pattern 132 has conductivity. In the reduction treatmentof the semiconductor pattern 132, the metallic component of thesemiconductor material, for example indium (In), is extracted to asurface of the semiconductor pattern 132. A thickness of the extractedmetal layer is less than about 200 nm. FIG. 9 shows an example of indium(In) particles extracted to the surface of the source region 133 and thedrain region 135 when the semiconductor material forming thesemiconductor pattern 132 includes indium (In). According to anexemplary embodiment of the present invention, a boundary between thechannel region 134 and the source region 133 or a boundary between thechannel region 134 and the drain region 135 is aligned or substantiallyaligned with an edge of the gate electrode 154 or the insulating layer142. However, in the reduction treatment of the semiconductor pattern132, a portion of the semiconductor pattern 132 under the edge portionof the insulating layer 142 may be reduced such that the boundarybetween the channel region 134 and the source region 133 or the drainregion 135 may be positioned more inwardly with respect to the edge ofthe gate electrode 154 or the insulating layer 142. Referring to FIG.10, an insulating material is coated on the gate electrode 154, thesource region 133, the drain region 135, and the buffer layer 120, thusforming the passivation layer 160. The passivation layer 160 ispatterned to form a contact hole 163 exposing the source region 133 anda contact hole 165 exposing the drain region 135. As shown in FIG. 1, adata input electrode 173 and a data output electrode 175 are formed onthe passivation layer 160. In the thin film transistor Q according to anexemplary embodiment of the present invention, the gate electrode 154and the source region 133 or the gate electrode 154 and the drain region135 do not overlap or substantially do not overlap each other such thatthe parasitic capacitance between the gate electrode 154 and the sourceregion 133 or between the gate electrode 154 and the drain region 135may be decreased. Accordingly, the on/off characteristics of the thinfilm transistor Q as a switching element may be improved. Referring toFIG. 11, a thin film transistor and a thin film transistor array panelaccording to an exemplary embodiment of the present invention aredescribed. FIG. 11 is a cross-sectional view including a thin filmtransistor array panel including a thin film transistor according to anexemplary embodiment of the present invention. Referring to FIG. 11, alight blocking film 70 is positioned on an insulation substrate 110. Thelight blocking film 70 prevents light from reaching a semiconductorincluded in the channel region 134 such that the semiconductor does notlose its characteristics. According to an embodiment, the light blockingfilm 70 is made of a material that does not transmit light of apredetermined wavelength band so that light does not reach thesemiconductor. According to an embodiment, the light blocking film 70 ismade of an organic insulating material, an inorganic insulatingmaterial, or a conductive material, such as a metal, and according to anembodiment, includes a single layer or multiple layers. A data line 115through which a data signal is transmitted is positioned on theinsulation substrate 110. According to an embodiment, the data line 115is made of a conductive material including metal, such as, e.g.,aluminum (Al), silver (Ag), copper (Cu), molybdenum (Mo), chromium (Cr),tantalum (Ta), and titanium (Ti), or alloys thereof. A buffer layer 120is positioned on the light blocking film 70 and the data line 115. Asemiconductor layer including a channel region 134, a source region 133,and a drain region 135 is formed on the buffer layer 120. The channelregion 134 includes an oxide semiconductor material. When the lightblocking film 70 is provided, the channel region 134 overlaps the lightblocking film 70. The source region 133 and the drain region 135 arepositioned at two sides of the channel region 134. The source region 133and the drain region 135 face each other and are separated from eachother with the channel region 134 positioned between the source region133 and the drain region 135. The source region 133 and the drain region135 are connected to the channel region 134. An insulating layer 142 ispositioned on the channel region 134. The insulating layer 142 coversthe channel region 134. According to an embodiment, the insulating layer142 does not overlap or substantially does not overlap the source region133 or the drain region 135. According to an embodiment, the insulatinglayer 142 has a single-layered structure or a multilayered structure.For example, according to an embodiment, the insulating layer 142includes a single layer including a material, such as silicon oxide(SiOx) or silicon nitride (SiNx), or includes a lower layer of aluminumoxide (Al₂O₃) and an upper layer of silicon oxide (SiOx). According toan embodiment, the insulating layer 142 has the characteristics of theinsulating layer 142 described in connection with FIGS. 1 to 10. A gateelectrode 154 is positioned on the insulating layer 142. An edge of thegate electrode 154 and an edge of the insulating layer 142 are alignedor substantially aligned with each other. The gate electrode 154includes a portion overlapping the channel region 134, and the channelregion 134 is covered by the gate electrode 154. The source region 133and the drain region 135 are positioned at two sides of the channelregion 134 with respect to the gate electrode 154, and the source region133 and the drain region 135 do not overlap or do not substantiallyoverlap the gate electrode 154. Accordingly, the parasitic capacitancebetween the gate electrode 154 and the source region 133 or theparasitic capacitance between the gate electrode 154 and the drainregion 135 may be decreased. The gate electrode 154, the source region133, and the drain region 135 form the thin film transistor Q along withthe channel region 134. A passivation layer 160 is positioned on thegate electrode 154, the source region 133, the drain region 135, and thebuffer layer 120. The passivation layer 160 has a contact hole 163exposing the source region 133 and a contact hole 165 exposing the drainregion 135. The buffer layer 120 and the passivation layer 160 include acontact hole 161 exposing the data line 115. An organic layer 180 isfurther positioned on the passivation layer 160. The organic layer 180includes an organic insulating material or a color filter material. Theorganic layer 180 has a flat surface. The organic layer 180 includes acontact hole 183, which exposes the source region 133 and corresponds tothe contact hole 163 of the passivation layer 160, a contact hole 185,which exposes the drain region 135 and corresponds to the contact hole165 of the passivation layer 160, and a contact hole 181 which exposesthe data line 115 and corresponds to the contact hole 161 of thepassivation layer 160 and the buffer layer 120. As shown in FIG. 11,edges of the contact holes 183, 185, and 181 of the organic layer 180are respectively aligned with edges of the contact holes 163, 165, and161 of the passivation layer 160. Alternatively, the edges of thecontact holes 163, 165, and 161 of the passivation layer 160 arerespectively positioned in a further inward position than the edges ofthe contact holes 183, 185, and 181 of the organic layer 180. Forexample, the contact holes 163, 165, and 161 of the passivation layer160 are respectively positioned within the contact holes 183, 185, and181 of the organic layer 180 when seen in plan view. A data inputelectrode 173, also referred to as a source electrode, and a data outputelectrode 175, also referred to as a drain electrode, are disposed onthe organic layer 180. The data input electrode 173 is electricallyconnected to the source region 133 of the thin film transistor Q throughthe contact hole 163 of the passivation layer 160 and the contact hole183 of the organic layer 180, and the data output electrode 175 iselectrically connected to the drain region 135 of the thin filmtransistor Q through the contact hole 165 of the passivation layer 160and the contact hole 185 of the organic layer 180. The data inputelectrode 173 is connected to the data line 115 through the contact hole161 of the passivation layer 160 and the contact hole 181 of the organiclayer 180. Accordingly, the source region 133 receives a data signalfrom the data line 115. According to an embodiment, the data outputelectrode 175 forms a pixel electrode that is used to control imagedisplay or the data output electrode 175 is connected to a separatepixel electrode (not shown). A method of manufacturing the thin filmtransistor array panel shown in FIG. 11 according to an exemplaryembodiment of the present invention is described with reference to FIG.12 to FIG. 20 as well as FIG. 11. FIG. 12, FIG. 13, FIG. 14, FIG. 15,FIG. 16, FIG. 17, FIG. 18, FIG. 19 and FIG. 20 are cross-sectional viewssequentially showing a method of manufacturing the thin film transistorarray panel shown in FIG. 11 according to an exemplary embodiment of thepresent invention,

Referring to FIG. 12, a light blocking film 70 made of an organicinsulating material, an inorganic insulating material, or a conductivematerial, such as a metal, is formed on an insulation substrate 110 ofglass or plastic. According to an embodiment, the formation of the lightblocking film 70 is omitted according to the condition. A metal isdeposited and patterned on the insulation substrate 110 to thereby forma data line 115. According to an embodiment, the sequence of forming thelight blocking film 70 and the data line 115 is changed. For example,the data line 115 is formed, and the light blocking film 70 is thenformed. Referring to FIG. 13, a buffer layer 120, a semiconductormaterial layer 130, an insulating material layer 140, and a gate layer150 are sequentially deposited on the light blocking film 70 and thedata line 115. The buffer layer 120 is formed by depositing aninsulating oxide, such as silicon oxide (SiOx), aluminum oxide (Al₂O₃),hafnium oxide (HfO₃), and yttrium oxide (Y₂O₃). A thickness of thebuffer layer 120 is in a range from more than about 500 μm to less thanabout 1 ρm, but is not limited thereto. The semiconductor material layer130 is formed by depositing an oxide semiconductor material, such aszinc oxide (ZnO), zinc-tin oxide (ZTO), zinc-indium oxide (ZIO), indiumoxide (InO), titanium oxide (TiO), indium-gallium-zinc oxide (IGZO), andindium-zinc-tin oxide (IZTO). The insulating material layer 140 isformed of an insulating material including an insulating oxide, such assilicon oxide (SiOx). According to an embodiment, the insulatingmaterial layer 140 includes a single-layered structure or a multilayeredstructure including a lower layer 140 a including an oxide, such assilicon oxide (SiOx), and an upper layer 140 b including an insulatingmaterial. A thickness of the insulating material layer 140 is in a rangefrom more than about 1000 Å to less than about 5000 Å, but is notlimited thereto. The gate layer 150 is formed by depositing a conductivematerial, such as aluminum (Al). Referring to FIG. 14, a photosensitivefilm of a photoresist is coated on the gate layer 150 and is exposed tolight, thereby forming the photosensitive film pattern 50. Thephotosensitive film pattern 50 includes, as shown in FIG. 14, a firstportion 52 having a relatively large thickness and a second portion 54having a relatively small thickness. The first portion 52 of thephotosensitive film pattern 50 overlaps the light blocking film 70. Twosides of the second portion 54, which are separated and face each otherwith respect to the first portion 52, are respectively connected to twosides of the first portion 52 of the photosensitive film pattern 50. Thephotosensitive film pattern 50 is formed by an exposing process using aphotomask (not shown) including a transflective region. For example, thephotomask for forming the photosensitive film pattern 50 includes atransmission region that transmits light, a light blocking region thatblocks light, and a transflective region that transmits part of light.According to an embodiment, the transflective region is formed of a slitor a translucent layer. When the exposing process is performed by usingthe photomask including the transflective region and using a negativephotosensitive film, a portion corresponding to the transmission regionof the photomask is irradiated with light such that the photosensitivefilm remains thereby forming the first portion 52 having a relativelylarge thickness, a portion corresponding to the light blocking region ofthe photomask is blocked from light irradiation such that thephotosensitive film is removed, and a portion corresponding to thetransflective region of the photomask is partially irradiated with lightsuch that the second portion 54 having a relatively small thickness isformed. When a positive photosensitive film is used for the exposingprocess, a portion corresponding to the transmission region of thephotomask is irradiated with light such that the photosensitive film isremoved, a portion corresponding to the light blocking region of thephotomask is blocked from light irradiation such that the photosensitivefilm remains thereby forming the first portion 52 having a relativelylarge thickness, and a portion corresponding to the transflective regionof the photomask is partially irradiated with light such that the secondportion 54 having a relatively small thickness is formed. As such,irrespective of whether a negative photosensitive film or positivephotosensitive film is used for the exposing process, the portioncorresponding to the transflective region of the photomask is subjectedto partial light irradiation, thus resulting in the second portion 54 ofthe photosensitive film pattern 50. Referring to FIG. 15, the gate layer150 and the insulating material layer 140 are sequentially etched byusing the photosensitive film pattern 50 as an etching mask. Accordingto an embodiment, the gate layer 150 is etched through a wet etchingmethod, and the insulating material layer 140 is etched through a dryetching method. Accordingly, the gate pattern 152 and the insulatingpattern 141 having the same plane shape are formed under thephotosensitive film pattern 50. The semiconductor material layer 130that is not covered by the photosensitive film pattern 50 is exposed.Referring to FIG. 16, the exposed semiconductor material layer 130 isremoved by using the gate pattern 152 and the insulating pattern 141 asan etching mask to thereby form a semiconductor pattern 132. Thesemiconductor pattern 132 has the same plane shape as the gate pattern152 and the insulating pattern 141. Referring to FIG. 17, thephotosensitive film pattern 50 is etched through an ashing method usingoxygen plasma so that the second portion 54 is removed and a thicknessof the photosensitive film pattern 50 is reduced. Accordingly, the firstportion 52 with the reduced thickness remains thereby resulting in aphotosensitive film pattern 50′. Referring to FIG. 18, the gate pattern152 and the insulating pattern 141 are sequentially etched by using thephotosensitive film pattern 50′ as an etching mask. Accordingly, thesemiconductor pattern 132 that is not covered by the photosensitive filmpattern 50′ is exposed. The exposed semiconductor pattern 132 ispositioned at two sides of the semiconductor pattern 132 that is coveredby the photosensitive film pattern 50′. Referring to FIG. 19, thesemiconductor pattern 132 undergoes a reduction treatment to therebyform the source region 133 and the drain region 135 having conductivity.The semiconductor pattern 132 covered by the insulating layer 142 is notreduced thereby forming the channel region 134. The gate electrode 154,the source region 133, and the drain region 135 form the thin filmtransistor Q along with the channel region 134. According to anembodiment, the reduction treatment method includes a heat treatmentmethod that is performed in a reduction atmosphere and a gas plasmatreatment using plasma, such as hydrogen (H₂), argon (Ar), nitrogen(N₂), nitrogen oxide (N₂O), and fluoroform (CHF₃). At least a portion ofthe semiconductor material forming the reduced and exposed semiconductorpattern 132 has only metallic bonding. Accordingly, the reducedsemiconductor pattern 132 has conductivity. In the reduction treatmentof the semiconductor pattern 132, the metallic component of thesemiconductor material, for example indium (In), is extracted to asurface of the semiconductor pattern 132. A thickness of the extractedmetal layer is less than about 200 nm. According to an exemplaryembodiment of the present invention, a boundary between the channelregion 134 and the source region 133 or a boundary between the channelregion 134 and the drain region 135 is aligned or substantially alignedwith an edge of the gate electrode 154 or the insulating layer 142.However, in the reduction treatment of the semiconductor pattern 132, aportion of the semiconductor pattern 132 under the edge portion of theinsulating layer 142 may be reduced such that the boundary between thechannel region 134 and the source region 133 or the drain region 135 maybe positioned more inwardly with respect to the edge of the gateelectrode 154 or the insulating layer 142. Referring to FIG. 20, afterremoving the photosensitive film pattern 50′, an insulating material iscoated on the gate electrode 154, the source region 133, the drainregion 135, and the buffer layer 120 to thereby form a passivation layer160. An organic insulating material is coated on the passivation layer160, thus forming the organic layer 180. As shown in FIG. 11, contactholes 163, 165, 161, 183, 185, and 181 are formed in the passivationlayer 160 and the organic layer 180, and a data input electrode 173 anda data output electrode 175 are formed on the organic layer 180. Whenforming the contact holes 163, 165, 161, 183, 185, and 181 in thepassivation layer 160 and the organic layer 180, one or two masks areused. For example, the organic layer 180 is exposed by using onephotomask to form the contact holes 183, 185, and 181 of the organiclayer 180, and then contact holes 163, 165, and 161 of the passivationlayer 160 are formed that, when viewed in plan view, are respectivelypositioned within the contact holes 183, 185, and 181 of the organiclayer 180 by using another photomask. Edges of the contact holes 163,165, and 161 of the passivation layer 160 are respectively aligned withedges of the contact holes 183, 185, and 181 of the organic layer 180.FIG. 21 is a graph illustrating a voltage-current characteristic of athin film transistor according to an exemplary embodiment of the presentinvention, and FIG. 22 is a graph illustrating a voltage-currentcharacteristic according to various source-drain voltages of a thin filmtransistor according to an exemplary embodiment of the presentinvention. Referring to FIG. 21, an on/off transition of thesource-drain current (Ids) according to the gate electrode voltage (Vg)in a thin film transistor Q according to an exemplary embodiment of thepresent invention is distinctly identified at a threshold voltage, andan ON current is relatively high, which means that the characteristicsof the thin film transistor Q as a switching element are improved.Referring to FIG. 22, a thin film transistor Q according to an exemplaryembodiment of the present invention experiences no or little change inthe threshold voltage according to a change in the source-drain voltage(Vds), such that the thin film transistor Q may maintain uniformcharacteristics as a switching element. As described above, according tothe exemplary embodiments of the present invention, the gate electrode154 and the source region 133 of the thin film transistor Q or the gateelectrode 154 and the drain region 135 of the thin film transistor Q donot overlap or substantially do not overlap each other such that theparasitic capacitance between the gate electrode 154 and the sourceregion 133 or the parasitic capacitance between the gate electrode 154and the drain region 135 may be decreased. Accordingly, the ON currentand the mobility of the thin film transistor may be increased and theon/off characteristics of the thin film transistor Q as a switchingelement may be improved. As a result, a display device with the thinfilm transistor may have a reduced RC delay. Accordingly, the thicknessof the driving signal lines may be decreased, thus resulting in savingsin manufacturing costs. Further, the characteristics of the thin filmtransistor itself are improved, resulting in a reduced size of the thinfilm transistor and an increased margin for forming a minute channel.

FIG. 23A is a cross-sectional view illustrating a thin film transistorarray panel including a thin film transistor according to an exemplaryembodiment of the present invention, and FIG. 23B is a plan viewillustrating a thin film transistor array panel as shown in FIG. 23A,according to an exemplary embodiment of the present invention.

Referring to FIG. 23A, a light blocking film 70 may be positioned on aninsulation substrate 110 made of glass or plastic. The light blockingfilm 70 prevents light from reaching an oxide semiconductor that is tobe deposited later, thus preventing characteristics of the oxidesemiconductor from being lost. The light blocking film 70 is made of amaterial that does not transmit light of a wavelength band to reach theoxide semiconductor. The light blocking film 70 may be made of anorganic insulating material, an inorganic insulating material, or aconductive material such as a metal, and the light blocking film 70 mayinclude a single layer or multiple layers.

However, the light blocking film 70 may be omitted according to acondition. For example, when light is not radiated to a place under theinsulation substrate 110, for example when the thin film transistoraccording to an exemplary embodiment of the present invention is usedfor an organic light emitting device, the light blocking film 70 may beomitted.

A buffer layer 120 is positioned on the light blocking film 70. Thebuffer layer 120 may include an insulating oxide such as a silicon oxide(SiO_(x)), aluminum oxide (Al₂O₃), hafnium oxide (HfO₃), and yttriumoxide (Y₂O₃). The buffer layer 120 prevents an impurity from flowingfrom the insulation substrate 110 into the semiconductor to be depositedlater, thus protecting the semiconductor and improving an interfacecharacteristic of the semiconductor. A thickness of the buffer layer 120is in a range of more than about 500 Å to less than about 1 μm, but isnot limited thereto.

A semiconductor 134, a source electrode 133, and a drain electrode 135are formed on the buffer layer 120.

The semiconductor 134 may include an oxide semiconductor material. Theoxide semiconductor material is a metal oxide semiconductor made of ametal oxide of zinc (Zn), indium (In), gallium (Ga), tin (Sn), ortitanium (Ti), or a combination of the metal of zinc (Zn), indium (In),gallium (Ga), tin (Sn), titanium (Ti), or metal oxides thereof. Forexample, the oxide semiconductor material may include at least one ofzinc oxide (ZnO), zinc-tin oxide (ZTO), zinc-indium oxide (ZIO), indiumoxide (InO), titanium oxide (TiO), indium-gallium-zinc oxide (IGZO), orindium-zinc-tin oxide (IZTO).

When the light blocking film 70 is provided, the semiconductor 134 maybe covered by the light blocking film 70.

Referring to FIGS. 23A and 23B, the source electrode 133 and the drainelectrode 135, respectively, are positioned at sides of thesemiconductor 134, and the source electrode 133 and the drain electrode135 are separated from each other.

The source electrode 133 and the drain electrode 135 have conductivity,and may include the same material as the semiconductor material of thesemiconductor 134 and a semiconductor material reduced from thesemiconductor material of the semiconductor 134. A metal such as indium(In) included in the semiconductor material may be extracted to thesurface of the source electrode 133 and the surface of the drainelectrode 135.

Low conductive regions 136 are respectively positioned between thesemiconductor 134 and the source electrode 133 and between thesemiconductor 134 and the drain electrode 135. The low conductive region136 positioned between the semiconductor 134 and the source electrode133 contacts the semiconductor 134 and the source electrode 133, and thelow conductive region 136 positioned between the semiconductor 134 andthe drain electrode 135 contacts the semiconductor 134 and the drainelectrode 135 to be connected thereto.

The carrier concentration of the low conductive region 136 is higherthan the carrier concentration of the semiconductor 134 but is lowerthan the carrier concentration of the source electrode 133 and the drainelectrode 135. The low conductive region 136 has a lower conductivitythan conductivities of the source electrode 133 and the drain electrode135. The carrier concentration of the low conductive region 136 may begradually decreased from the source electrode 133 and the drainelectrode 135 toward the semiconductor 134.

A metal such as indium (In) included in the semiconductor material maybe extracted to the surface of the low conductive region 136.

An insulating layer 142 is positioned on the semiconductor 134. Theinsulating layer 142 may cover the semiconductor 134 and the lowconductive region 136. The insulating layer 142 might not substantiallyoverlap the source electrode 133 or the drain electrode 135.

The insulating layer 142 may be a singular layer or may include at leasttwo layers.

When the insulating layer 142 is a singular layer, the insulating layer142 may include an insulating oxide such as a silicon oxide (SiO_(x)),aluminum oxide (Al₂O₃), hafnium oxide (HfO₃), and yttrium oxide (Y₂O₃).The insulating layer 142 may improve interface characteristics of thesemiconductor 134 and may prevent an impurity from penetrating into thesemiconductor 134.

When the insulating layer 142 has a multilayered structure, theinsulating layer 142 may include a lower layer 142 a and an upper layer142 b shown in FIG. 23A. The lower layer 142 a includes an insulatingoxide such as a silicon oxide (SiO_(x)), aluminum oxide (Al₂O₃), hafniumoxide (HfO₃), and yttrium oxide (Y₂O₃), and thus, the interfacecharacteristics of the semiconductor 134 may be improved and thepenetration of an impurity into the semiconductor 134 may be prevented.The upper layer 142 b may be made of various insulating materials suchas a silicon nitride (SiN_(x)) and a silicon oxide (SiO_(x)). Forexample, the insulating layer 142 may include a lower layer of analuminum oxide (AlO_(x)) and an upper layer of a silicon oxide(SiO_(x)). The thickness of the lower layer may be less than about 500Å, and the thickness of the upper layer may be more than about 500 Å andless than about 1500 Å, but is not limited thereto. As another example,the insulating layer 142 may include a lower layer of silicon oxide(SiO_(x)) and an upper layer of silicon nitride (SiNx). The thickness ofthe lower layer may be about 2000 Å, and the thickness of the upperlayer may be about 1000 Å, but is not limited thereto.

The thickness of the insulating layer 142 may be more than about 1000 Åand less than about 5000 Å, but is not limited thereto. The thickness ofthe insulating layer 142 may be controlled, maximizing thecharacteristics of the thin film transistor.

A gate electrode 154 is positioned on the insulating layer 142. An edgeboundary of the gate electrode 154 is positioned inside an edge boundaryof the insulating layer 142. Accordingly, the insulating layer 142includes an outer boundary portion 144 that is not covered by the gateelectrode 154. The outer boundary portion 144 overlaps the lowconductive region 136 and covers the low conductive region 136. The edgeboundary of the outer boundary portion 144 and the edge boundary of thelow conductive region 136 may be substantially aligned with each other.

A width d1 of a lower end of the outer boundary portion 144 is largerthan 0, and may be controlled according to a required length of the lowconductive region 136.

The width d3 of the lower end of the insulating layer 142 in the channellength direction may be larger than the width d2 of the lower end of thegate electrode 154 in the channel length direction and may be smallerthan about three times the width d2 of the lower end of the gateelectrode 154 in the channel length direction.

Referring to FIGS. 23A and 23B, the gate electrode 154 overlaps thesemiconductor 134 and covers the semiconductor 134. Low conductiveregions 136 are positioned at two opposite sides of the semiconductor134 with respect to the gate electrode 154, and the source electrode 133and the drain electrode 135 are positioned at sides the low conductiveregion 136. The low conductive region 136, the source electrode 133, andthe drain electrode 135 do not substantially overlap the gate electrode154. Accordingly, the parasitic capacitance between the gate electrode154 and the source electrode 133 or the parasitic capacitance betweenthe gate electrode 154 and the drain electrode 135 may be decreased.

The gate electrode 154 may be made of a metal such as aluminum (Al),silver (Ag), copper (Cu), molybdenum (Mo), chromium (Cr), tantalum (Ta),titanium (Ti), or alloys thereof. The gate electrode 154 may have asingle-layered or multilayered structure. The multilayered structure maybe a dual-layered structure including a lower layer of titanium (Ti),tantalum (Ta), molybdenum (Mo), or ITO and an upper layer such as copper(Cu), and a triple-layered structure of molybdenum (Mo)-aluminum(Al)-molybdenum (Mo). However, the gate electrode 154 may be made ofvarious metals or conductors.

According to an exemplary embodiment of the present invention, theboundary between the low conductive region 136 and the source electrode133 may be substantially aligned with the edge boundary of theinsulating layer 142, and the edge boundary of the gate electrode 154may be substantially aligned with the boundary between the semiconductor134 and the low conductive region 136.

The gate electrode 154, the source electrode 133, and the drainelectrode 135, along with the semiconductor 134, form a thin filmtransistor (TFT) Q. The channel of the thin film transistor Q is formedin the semiconductor 134.

According to an exemplary embodiment of the present invention, the lowconductive region 136 may increase the resistance to a current flowingfrom the source electrode 133 or the drain electrode 135 to thesemiconductor 134. For example, the low conductive region 136 may have afunction substantially corresponding to a lightly doped drain (LDD)region of a metal oxide silicon field effect transistor (MOSFET).

For example, when the size of the thin film transistor Q is graduallydecreased and thus the channel length of the thin film transistor Q isdecreased, the electric field between the source electrode 133 and thedrain electrode 135 is increased, and thus, mobility of the carrier maybe excessively increased. Thus, hot carriers may be generated. The hotcarriers may exit the insulating layer 142. The hot carriers may also beaccumulated in the insulating layer 142, thus deteriorating theelectrical characteristics of the thin film transistor Q.

However, according to an exemplary embodiment of the present invention,when the low conductive region 136 is formed by forming the outerboundary portion 144 of the insulating layer 142, the carrierconcentration is gradually varied between the semiconductor 134 and thesource electrode 133 or the drain electrode 135, and thus, thegeneration of the hot carriers may be suppressed and the channel lengthof the semiconductor 134 may be prevented from being decreased.Accordingly, a drastic increase in current to the semiconductor 134 maybe prevented, and the characteristics of the thin film transistor Q maybe stabilized and improved.

The distance between the gate electrode 154 and the source electrode 133or the drain electrode 135 may be increased by the outer boundaryportion 144 of the insulating layer 142, and thus, a leakage pathbetween the gate electrode 154 and the source electrode 133 or the drainelectrode 135 may be increased and a short circuit between the gateelectrode 154 and the source electrode 133 or the drain electrode 135may be prevented. Accordingly, the thickness of the insulating layer 142may be further decreased, and thus, an on-current of the thin filmtransistor Q may be increased.

A passivation layer 160 is positioned on the gate electrode 154, thesource electrode 133, the drain electrode 135, and the buffer layer 120.The passivation layer 160 may be made of an inorganic insulatingmaterial such as a silicon nitride or silicon oxide, or an organicinsulating material. The passivation layer 160 has a contact hole 163exposing the source electrode 133 and a contact hole 165 exposing thedrain electrode 135.

A data input electrode 173 and a data output electrode 175 may bepositioned on the passivation layer 160. The data input electrode 173 iselectrically connected to the source electrode 133 of the thin filmtransistor Q through the contact hole 163 of the passivation layer 160,and the data output electrode 175 is electrically connected to the drainelectrode 135 of the thin film transistor Q through the contact hole 165of the passivation layer 160.

Alternatively, a color filter (not shown) or an organic layer (notshown) made of an organic material may be further positioned on thepassivation layer 160, and the data input electrode 173 and the dataoutput electrode 175 may be positioned on the color filter or organiclayer.

FIG. 24 to FIG. 33 are cross-sectional views sequentially showing amethod of manufacturing a thin film transistor array panel as shown inFIG. 23, according to an exemplary embodiment of the present invention.

Referring to FIG. 24, the light blocking film 70 made of an organicinsulating material, an inorganic insulating material, or a conductivematerial such as a metal is formed on the insulation substrate 110 madeof glass or plastic. Alternatively, forming of the light blocking film70 may be omitted.

Referring to FIG. 25, the buffer layer 120 made of an insulatingmaterial including an oxide such as a silicon oxide (SiO_(x)), aluminumoxide (Al₂O₃), hafnium oxide (HfO₃), and yttrium oxide (Y₂O₃) is formedon the light blocking film 70 by a chemical vapor deposition (CVD)method. A thickness of the buffer layer 120 is in a range of more thanabout 500 Å and less than about 1 μm, but is not limited thereto.

Referring to FIG. 26, the semiconductor layer 130 made of an oxidesemiconductor material such as zinc oxide (ZnO), zinc-tin oxide (ZTO),zinc-indium oxide (ZIO), indium oxide (InO), titanium oxide (TiO),indium-gallium-zinc oxide (IGZO), or indium-zinc-tin oxide (IZTO) iscoated on the buffer layer 120.

A photosensitive film of a photoresist is coated on the semiconductorlayer 130 and is exposed, forming a photosensitive film pattern 50. Thephotosensitive film pattern 50 may overlap at least a portion of thelight blocking film 70.

Referring to FIG. 27, the semiconductor layer 130 is etched by using thephotosensitive film pattern 50 as a mask, forming a semiconductorpattern 132.

An insulating material layer 140 is formed on the semiconductor pattern132 and the buffer layer 120. The insulating material layer 140 may be asingle layer including an insulating oxide of silicon oxide (SiO_(x)),or as shown in FIG. 27, the insulating material layer 140 may include amultilayered structure including a lower layer 140 a including aninsulating oxide such as a silicon oxide (SiO_(x)) and the upper layer140 b including an insulating material. The thickness of the insulatingmaterial layer 140 may be more than about 1000 Å and less than about5000 Å, but is not limited thereto.

Referring to FIG. 28, a conductive material such as a metal is depositedon the insulating material layer 140 and the deposited conductivematerial is patterned, forming a gate layer 150. A photosensitive filmis coated on the gate layer 150 and is exposed, forming a photosensitivefilm pattern 50. The photosensitive film pattern 50 overlaps a portionof the semiconductor pattern 132.

Referring to FIG. 29, the gate layer 150 is etched by using thephotosensitive film pattern 50 as a mask, forming the gate electrode154. A wet etching method may be used, and the edge boundary of the gateelectrode 154 is formed inside the edge boundary of the photosensitivefilm pattern 50 by controlling the degree of the etching. The gateelectrode 154 is formed, crossing a middle portion of the semiconductorpattern 132, and thus two portions of the semiconductor pattern 132positioned on two opposite sides of the overlapping portion of the gateelectrode 154 and the semiconductor pattern 132 are not covered by thegate electrode 154.

Referring to FIG. 30, the insulating material layer 140 is patterned byusing the gate electrode 154 as an etching mask, forming the insulatinglayer 142. A dry etching method may be used. The edge boundary of theinsulating layer 142 is formed outside the edge boundary of the gateelectrode 154. Also, the buffer layer 120 might not be etched bycontrolling an etching gas and an etching time.

Two portions of the semiconductor pattern 132 that are covered by theinsulating layer 142 are positioned at two opposite sides of theoverlapping portion of the insulating layer 142 and the semiconductorpattern 132.

The insulating layer 142 may be a single layer, or the insulating layer142 may include a double-layered structure including the lower layer 142a including an insulating oxide and the upper layer 142 b including aninsulating material.

Referring to FIG. 31, the photosensitive film pattern 50 is removed.Before the removal of the photosensitive film pattern 50, an ashingprocess may be performed using an oxygen gas.

Referring to FIG. 32, the two exposed portion of the semiconductorpattern 132 are reduced, forming the source electrode 133 and the drainelectrode 135 having conductivity. The region of the semiconductorpattern 132 that does not overlap the gate electrode 154 and overlapsthe insulating layer 142, for example, the region of the semiconductorpattern 132 overlapping the outer boundary portion 144 of the insulatinglayer 142, is subjected to reduction whose level decreases towards theinside of the semiconductor pattern 132, forming the low conductiveregion 136. The semiconductor pattern 132 overlapping the gate electrode154 becomes the semiconductor 134.

A heat treatment method may be used in a reduction atmosphere, reducingthe exposed semiconductor pattern 132. Alternatively, a gas plasma usinga plasma such as hydrogen (H₂), helium (He), phosphine (PH₃), ammonia(NH₃), silane (SiH₄), methane (CH₄), acetylene (C₂H₂), diborane (B₂H₆),carbon dioxide (CO₂), germane (GeH₄), hydrogen selenide (H₂Se), hydrogensulfide (H₂S), argon (Ar), nitrogen (N₂), nitrogen oxide (N₂O), andfluoroform (CHF₃) may be used, thus reducing the exposed semiconductorpattern 132.

At least a portion of the semiconductor material forming the reduced andexposed semiconductor pattern 132 may be reduced, leaving a metallicbond. Accordingly, the reduced semiconductor pattern 132 hasconductivity, forming the source electrode 133 and the drain electrode135.

A gas such as hydrogen penetrates into the semiconductor pattern 132overlapping the outer boundary portion 144 of the insulating layer 142during the reduction treatment, and thus, the semiconductor pattern 132is reduced to some degree. The carrier concentration of the lowconductive region 136 formed may be gradually decreased according to thedegree of the penetration degree of the gas.

During the reduction treatment of the semiconductor pattern 132, themetal component of the semiconductor material, for example, indium (In),may be extracted to the surface on the semiconductor pattern 132. Thethickness of the extracted metal layer may be less than about 200 nm.

FIG. 34 and FIG. 35 are photos showing cross-sections of a thin filmtransistor according to an exemplary embodiment of the presentinvention.

Referring to FIG. 34, indium (In) particles are extracted to the surfaceof the source electrode 133 and the drain electrode 135 when thesemiconductor material forming the semiconductor pattern 132 includesindium (In).

Referring to FIG. 35, indium (In) is extracted to a space between theouter boundary portion 144 of the insulating layer 142 and the lowconductive region 136

The gate electrode 154, the source electrode 133, and the drainelectrode 135, along with the semiconductor 134, form the thin filmtransistor Q.

Referring to FIG. 33, an insulating material is coated on the gateelectrode 154, the source electrode 133, the drain electrode 135, andthe buffer layer 120, forming the passivation layer 160. The passivationlayer 160 is patterned, forming a contact hole 163 exposing the sourceelectrode 133 and a contact hole 165 exposing the drain electrode 135.

As shown in FIG. 23, a data input electrode 173 and a data outputelectrode 175 may be formed on the passivation layer 160.

In the thin film transistor Q according to an exemplary embodiment ofthe present invention, the gate electrode 154 does not substantiallyoverlap the source electrode 133 or the drain electrode 135, and thus,the parasitic capacitance between the gate electrode 154 and the sourceelectrode 133 or between the gate electrode 154 and the drain electrode135 may be very small. Accordingly, the on/off characteristics of thethin film transistor Q as a switching element may be improved.

The insulating layer 142 is patterned by using the photosensitive filmpattern 50 for forming the gate electrode 154, thus forming theinsulating layer 142 having a wider width than the gate electrode 154,and the semiconductor pattern 132 is reduced, and thus, the insulatinglayer 142 may form the low conductive region 136 under the outerboundary portion 144. Accordingly, the channel length of the thin filmtransistor semiconductor 134 may be prevented from decreasing, hotcarriers may be suppressed from being generated, the current to thesemiconductor 134 may be prevented from increasing, and thecharacteristics of the thin film transistor Q may be stabilized andimproved.

The distance between the gate electrode 154 and the source electrode 133or the drain electrode 135 may be increased by the outer boundaryportion 144 of the insulating layer 142, and thus, the leakage pathbetween the gate electrode 154 and the source electrode 133 or the drainelectrode 135 may be increased, and a short circuit between the gateelectrode 154 and the source electrode 133 or the drain electrode 135may be prevented from being formed. Accordingly, the thickness of theinsulating layer 142 may be further decreased.

FIG. 36 and FIG. 37 are photos showing cross-sections of a thin filmtransistor according to an exemplary embodiment of the presentinvention, and FIG. 38 is an enlarged view of a thin film transistorshown in FIG. 37, according to an exemplary embodiment of the presentinvention.

In the method of manufacturing the described thin film transistor, whenperforming the ashing process using oxygen before removing thephotosensitive film pattern 50 and after forming the gate electrode 154,the metal component of the gate electrode 154 may be adhered to thesurface of the insulating layer 142. FIG. 36 shows a shape of the metalcomponent, e.g., copper (Cu), of the gate electrode 154 adhered to aside surface of the insulating layer 142 when the edge boundaries of thegate electrode 154 and the insulating layer 142 are substantiallyaligned with each other when the insulating layer 142 does not includethe outer boundary portion 144. In this case, the gate electrode 154 maybe shorted to the source electrode 133 or the drain electrode 135.

However, referring to FIG. 37 and FIG. 38, in an exemplary embodiment ofthe present invention, when the outer boundary portion 144 of theinsulating layer 142 is formed, although the metal component, e.g.,copper (Cu), of the gate electrode 154 is emitted, the metal componentmay be adhered to an upper surface of the outer boundary portion 144.Accordingly, the gate electrode 154 is less likely to be shorted to thesource electrode 133 or the drain electrode 135, and the distancebetween the gate electrode 154 and the source electrode 133 or the drainelectrode 135 is increased by the outer boundary portion 144 of theinsulating layer 142, thus decreasing the possibility of a shortcircuit.

FIG. 39 and FIG. 40 are graphs showing on-current characteristicsaccording to gate voltages of a thin film transistor according to anexemplary embodiment of the present invention.

FIG. 39 shows a source-drain current Ids when a source-drain voltage Vdsis about 10 V, and FIG. 40 shows a source-drain current Ids when asource-drain voltage Vds is about 0.1 V.

Referring to FIG. 39 and FIG. 40, the turn on and turn off of thesource-drain current Ids according to the gate electrode voltage Vg ofthe thin film transistor Q according to an exemplary embodiment of thepresent invention are clearly distinguished from each other with respectto a threshold voltage, and the on-current is relatively high, and thus,characteristics of the thin film transistor Q as a switching element ofthe thin film transistor Q is improved. Little change occurs in thethreshold voltage according to a change in the source-drain voltage, andthus, the characteristics of the switching element may be maintained.

FIG. 41 is a cross-sectional view of a thin film transistor array panelincluding a thin film transistor according to an exemplary embodiment ofthe present invention,

Referring to FIG. 41, the light blocking film 70 may be positioned onthe insulation substrate 110.

A data line 115 through which a data signal is transmitted may bepositioned on the insulation substrate 110. The data line 115 may bemade of a conductive material, e.g., a metal such as aluminum (Al),silver (Ag), copper (Cu), molybdenum (Mo), chromium (Cr), tantalum (Ta),and titanium (Ti), or alloys thereof.

The buffer layer 120 is positioned on the light blocking film 70 and thedata line 115.

The semiconductor 134, the low conductive region 136, the sourceelectrode 133, and the drain electrode 135 are formed on the bufferlayer 120.

The semiconductor 134 may include an oxide semiconductor material. Thesemiconductor 134 may be covered by the light blocking film 70.

The source electrode 133 and the drain electrode 135 are positioned attwo opposite sides with respect to the semiconductor 134 and face eachother. The source electrode 133 and the drain electrode 135 areseparated from each other. The low conductive region 136 is positionedbetween the semiconductor 134 and the source electrode 133 or the drainelectrode 135. The low conductive region 136 has conductivity. Thecarrier concentration of the low conductive region 136 is smaller thanthe carrier concentration of the source electrode 133 or the drainelectrode 135. The carrier concentration of the low conductive region136 may be gradually decreased toward the semiconductor 134 from thesource electrode 133 or the drain electrode 135.

The insulating layer 142 is positioned on the semiconductor 134 and thelow conductive region 136. The insulating layer 142 may cover thesemiconductor 134 and the low conductive region 136. The insulatinglayer 142 might not substantially overlap the source electrode 133 orthe drain electrode 135. The insulating layer 142 may be a single layeror include a multilayer structure. For example, the insulating layer 142may be a single layer such as a silicon oxide (SiO_(x)) or siliconnitride (SiN^(x)), and may include a lower layer of aluminum oxide(Al₂O₃) and an upper layer of silicon oxide (SiO_(x)). Thecharacteristics of the insulating layer 142, described above inconnection with FIGS. 23A to 40 may be applied to the insulating layer142 illustrated in FIG. 41.

The gate electrode 154 is positioned on the insulating layer 142. Theedge boundary of the gate electrode 154 is positioned inside the edgeboundary of the insulating layer 142, and the insulating layer 142 thatis covered by the gate electrode 154 forms the outer boundary portion144.

The gate electrode 154 includes a portion overlapping the semiconductor134, and the semiconductor 134 is covered by the gate electrode 154. Theouter boundary portion of the insulating layer 142 overlaps the lowconductive region 136.

The low conductive region 136, the source electrode 133, and the drainelectrode 135 are disposed at two opposite sides of the semiconductor134 with respect to the gate electrode 154, and the source electrode 133and the drain electrode 135 might not substantially overlap the gateelectrode 154.

The gate electrode 154, the source electrode 133, and the drainelectrode 135, along with the semiconductor 134, form the thin filmtransistor Q.

The passivation layer 160 is positioned on the gate electrode 154, thesource electrode 133, the drain electrode 135, and the buffer layer 120.The passivation layer 160 may have the contact hole 163 exposing thesource electrode 133 and the contact hole 165 exposing the drainelectrode 135. The buffer layer 120 and the passivation layer 160 mayinclude a contact hole 161 exposing the data line 115.

An organic layer 180 may be further positioned on the passivation layer160. The organic layer 180 may include an organic insulating material ora color filter material. The organic layer 180 may have a flat surface.The organic layer 180 may include a contact hole 183 exposing the sourceelectrode 133 and corresponding to the contact hole 163 of thepassivation layer 160, a contact hole 185 exposing the drain electrode135 and corresponding to the contact hole 165 of the passivation layer160, and a contact hole 181 exposing the data line 115 and correspondingto the contact hole 161 of the passivation layer 160 and the bufferlayer 120. As shown in FIG. 41, respective edges of the contact holes183, 185, and 181 of the organic layer 180 are respectively aligned withrespective edges of the contact holes 163, 165, and 161 of thepassivation layer 160. However, the respective edges of the contactholes 163, 165, and 161 of the passivation layer 160 may be respectivelypositioned inside the respective edges of the contact holes 183, 185,and 181 of the organic layer 180. For example, the contact holes 163,165, and 161 of the passivation layer 160 may be respectively positionedinside the respective edges of the contact holes 183, 185, and 181 ofthe organic layer 180.

The data input electrode 173 and the data output electrode 175 may bepositioned on the organic layer 180. The data input electrode 173 iselectrically connected to the source electrode 133 of the thin filmtransistor Q through the contact hole 163 of the passivation layer 160and the contact hole 183 of the organic layer 180, and the data outputelectrode 175 is electrically connected to the drain electrode 135 ofthe thin film transistor Q through the contact hole 165 of thepassivation layer 160 and the contact hole 185 of the organic layer 180.The data input electrode 173 may be connected to the data line 115through the contact hole 161 of the passivation layer 160 and thecontact hole 181 of the organic layer 180. Accordingly, the sourceelectrode 133 may receive a data signal from the data line 115. The dataoutput electrode 175 forms a pixel electrode, controlling displaying animage, or the data output electrode 175 may be connected to a separatepixel electrode (not shown).

FIG. 42 to FIG. 49 are views sequentially showing a method ofmanufacturing a thin film transistor array panel shown in FIG. 41,according to an exemplary embodiment of the present invention.

Referring to FIG. 42, a light blocking film 70 made of an organicinsulating material, an inorganic insulating material, or a conductivematerial such as a metal is formed on an insulation substrate 110 madeof glass or plastic. Alternatively, the formation of the light blockingfilm 70 may be omitted.

A metal layer is deposited and patterned on the insulation substrate110, forming the data line 115. The sequence in which the light blockingfilm 70 and the data line 115 are formed may be changed.

Referring to FIG. 43, a buffer layer 120, a semiconductor layer 130, aninsulating material layer 140, and a gate layer 150 are sequentiallydeposited on the light blocking film 70 and the data line 115.

The buffer layer 120 may be formed by depositing an insulating oxidesuch as silicon oxide (SiO_(x)), aluminum oxide (Al₂O₃), hafnium oxide(HfO₃), or yttrium oxide (Y₂O₃), and the thickness of the buffer layer120 may be in a range from more than about 500 Å to less than about 1μm, but is not limited thereto.

The semiconductor layer 130 may be formed by depositing an oxidesemiconductor material such as zinc oxide (ZnO), zinc-tin oxide (ZTO),zinc-indium oxide (ZIO), indium oxide (InO), titanium oxide (TiO),indium-gallium-zinc oxide (IGZO), or indium-zinc-tin oxide (IZTO).

The insulating material layer 140 may be formed of an insulatingmaterial including an insulating oxide such as a silicon oxide(SiO_(x)). The insulating material layer 140 may be a single layer ormay include a multilayered structure including a lower layer 140 aincluding an oxide such as a silicon oxide (SiO_(x)) and an upper layer140 b including an insulating material. The thickness of the insulatingmaterial layer 140 may be in a range from more than about 1000 Å to lessthan about 5000 Å, but is not limited thereto.

The gate layer 150 may be formed by depositing a conductive materialsuch as aluminum (Al).

Referring to FIG. 44, a photosensitive film such as a photoresist layeris coated on the gate layer 150 and is exposed to light, forming thephotosensitive film pattern 50. The photosensitive film pattern 50includes, as shown in FIG. 44, a first portion 52 having a relativelythin thickness and a second portion 54 having a relatively thickthickness. The first portion 52 of the photosensitive film pattern 50may be positioned at a portion overlapping the light blocking film 70.Second portions 54 that are separated from each other and face eachother with respect to the first portion 52 are connected to two oppositesides, respectively, of the first portion 52 of the photosensitive filmpattern 50.

The photosensitive film pattern 50 may be formed by exposing thephotosensitive film to light through a photomask (not shown) including atransflective region. For example, the photomask for forming thephotosensitive film pattern 50 may include a transmission regiontransmitting light, a light blocking region which does not transmitlight, and a transflective region which partially transmits light. Thetransflective region may be formed by using a slit or a translucentlayer.

When a negative photosensitive film is exposed to light by the photomaskincluding the transflective region, a portion corresponding to atransmission region of the photomask is irradiated with light, formingthe first portion 52 that is relatively thick. A portion correspondingto the light blocking region of the photomask is not irradiated withlight, and thus, the photosensitive film is removed. A portioncorresponding to the transflective region of the photomask is partiallyirradiated with the light, thus forming the second portion 54 that isrelatively thin. For example, when a positive photosensitive film isused for the exposure, the portion corresponding to the transmissionregion of the photomask leaves the photosensitive film removed, and theportion corresponding to the light blocking region of the photomask mayleaves the first portion 52 relatively thick. The portion correspondingto the transflective region of the photomask is partially irradiated,thus forming the second portion 54 of the photosensitive film pattern50.

Referring to FIG. 45, the gate layer 150 and the insulating materiallayer 140 are sequentially etched by using the photosensitive filmpattern 50 as an etching mask. The gate layer 150 may be etched througha wet etching method, and the insulating material layer 140 may beetched through a dry etching method. Accordingly, a gate pattern 152 andan insulating pattern 141 having substantially the same plane shape maybe formed under the photosensitive film pattern 50. The semiconductorlayer 130 that is not covered by the photosensitive film pattern 50 maybe exposed.

Referring to FIG. 46, the exposed semiconductor layer 130 is removed byusing the gate pattern 152 and the insulating pattern 141 as an etchingmask, forming a semiconductor pattern 132. The semiconductor pattern 132may have the substantially same plane shape as the gate pattern 152 andthe insulating pattern 141.

Referring to FIG. 47, the entire photosensitive film pattern 50 isetched through an ashing method using oxygen plasma, removing the secondportion 54. Accordingly, the first portion 52 with a reduced thicknessand a photosensitive film pattern 50′ remain.

The gate pattern 152 is etched by using the photosensitive film pattern50′ as an etching mask, forming the gate electrode 154. The used etchingmay be wet etching, and the edge boundary of the gate electrode 154 ispositioned inside the edge boundary of the photosensitive film pattern50 by controlling the etching degree.

Referring to FIG. 48, the insulating pattern 141 is etched by using thephotosensitive film pattern 50′ as an etching mask, forming theinsulating layer 142 including the outer boundary portion 144. The usedetching may be a dry etching method. The edge boundary of the insulatinglayer 142 is formed outside the edge boundary of the gate electrode 154.

Accordingly, the semiconductor pattern 132 is not covered by theinsulating layer 142, but is exposed. The exposed semiconductor pattern132 is positioned at two opposite sides with respect to thesemiconductor pattern 132 that is covered by the insulating layer 142.

Referring to FIG. 49, the semiconductor pattern 132 undergoes areduction treatment, forming the source electrode 133, the drainelectrode 135, and the low conductive region 136 having conductivity.

A heat treatment method may be used in a reduction atmosphere as thereduction treatment method of the exposed semiconductor pattern 132, andgas plasma using plasma such as hydrogen (H₂), argon (Ar), nitrogen(N₂), nitrogen oxide (N₂O), and fluoroform (CHF₃) may be used. At leasta portion of the semiconductor material forming the reduced and exposedsemiconductor pattern 132 may be reduced, forming a metallic bond.Accordingly, the reduced semiconductor pattern 132 has conductivity. Inthe reduction treatment of the semiconductor pattern 132, the metalcomponent, e.g., indium (In), of the semiconductor material may beextracted to the surface on the semiconductor pattern 132. The thicknessof the extracted metal layer may be less than about 200 nm.

In the reduction treatment, plasma gas such as hydrogen penetrates intoa space under the outer boundary portion 144 of the insulating layer142, forming the low conductive region 136 in which the carrierconcentration is gradually decreased as the plasma gas penetratesdeeper. The semiconductor pattern 132 overlapping the gate electrode 154is not reduced, forming the semiconductor 134.

The gate electrode 154, the source electrode 133, and the drainelectrode 135, along with the semiconductor 134, form the thin filmtransistor Q.

Referring back to FIG. 41, after removing the photosensitive filmpattern 50′, an insulating material is coated on the gate electrode 154,the source electrode 133, the drain electrode 135, and the buffer layer120, forming the passivation layer 160. An organic insulating materialis coated on the passivation layer 160, additionally forming the organiclayer 180.

The contact holes 163, 165, 161, 183, 185, and 181 are formed in thepassivation layer 160 and the organic layer 180, and the data inputelectrode 173 and the data output electrode 175 are formed on theorganic layer 180.

When forming the contact holes 163, 165, 161, 183, 185, and 181 in thepassivation layer 160 and the organic layer 180, one or two masks may beused. For example, the organic layer 180 is exposed by using onephotomask, forming the contact holes 183, 185, and 181 of the organiclayer 180. Contact holes 163, 165, and 161 of the passivation layer 160are formed inside the contact holes 183, 185, and 181, respectively, ofthe organic layer 180 by using a photomask. The respective edges of thecontact holes 163, 165, and 161 of the passivation layer 160 may berespectively aligned with the respective edges of the contact holes 183,185, and 181 of the organic layer 180, and the respective edges of thecontact holes 163, 165, and 161 of the passivation layer 160 may berespectively positioned inside the respective edges of the contact holes183, 185, and 181 of the organic layer 180.

While the invention has been shown and described with reference toexemplary embodiments thereof, it is to be understood by one of ordinaryskill in the art that various changes in form and detail may be madethereto without departing from the spirit and scope of the invention asdefined by the following claims.

What is claimed is:
 1. A thin film transistor, comprising: a lightblocking layer; an oxide semiconductor disposed on the light blockinglayer; a source region and a drain region positioned at two oppositesides with respect to the oxide semiconductor and positioned at a samelayer as the oxide semiconductor; an insulating layer which ispositioned on and covers the oxide semiconductor; a gate electrodepositioned on the insulating layer, the light blocking layer overlappingthe gate electrode with the oxide semiconductor interposed between thegate electrode and the light blocking layer; a passivation layerdisposed on the gate electrode; and a data input electrode and a dataoutput electrode disposed on the passivation layer, wherein the datainput electrode is connected to the source region, and the data outputelectrode is connected to the drain region, wherein an edge boundary ofthe gate electrode is positioned inside an edge boundary of theinsulating layer, wherein the edge boundary of the insulating layer ispositioned inside an edge boundary of the light blocking layer, andwherein the passivation layer directly contacts a side surface of theinsulating layer and a side surface of the gate electrode.
 2. The thinfilm transistor of claim 1, further comprising a low conductive regionpositioned between the source region or the drain region and the oxidesemiconductor, wherein the insulating layer covers the oxidesemiconductor and the low conductive region, a carrier concentration ofthe low conductive region is lower than a carrier concentration of thesource region or the drain region, and the carrier concentration of thelow conductive region is gradually varied in the low conductive region.3. The thin film transistor of claim 2, wherein the edge boundary of theinsulating layer is substantially aligned to a boundary between the lowconductive region and the source region or the drain region.
 4. The thinfilm transistor of claim 3, wherein the edge boundary of the gateelectrode is substantially aligned to an edge boundary of the oxidesemiconductor.
 5. The thin film transistor of claim 1, furthercomprising a buffer layer disposed between the light blocking layer andthe oxide semiconductor.
 6. The thin film transistor of claim 5, whereinthe buffer layer or the insulating layer includes an insulating oxide.7. A thin film transistor, comprising: an insulation substrate; a lightblocking layer; an oxide semiconductor positioned on the light blockinglayer; a source region and a drain region positioned at two oppositesides with respect to the oxide semiconductor and positioned at a samelayer as the oxide semiconductor; an insulating layer which ispositioned on and covers the oxide semiconductor, a gate electrodepositioned on the insulating layer, the light blocking layer overlappingthe gat electrode with the oxide semiconductor interposed between thegate electrode and the light blocking layer; a passivation layerdisposed on the gate electrode; and a data input electrode and a dataoutput electrode disposed on the passivation layer, wherein the datainput electrode is connected to the source region, and the data outputelectrode is connected to the drain region, wherein an edge boundary ofthe gate electrode is positioned inside an edge boundary of theinsulating layer, wherein the edge boundary of the insulating layer ispositioned inside an edge boundary of the light blocking layer, andwherein the passivation layer directly contacts a side surface of theinsulating layer and a side surface of the gate electrode.
 8. The thinfilm transistor of claim 7, further comprising a low conductive regionpositioned between the source region or the drain region and the oxidesemiconductor, wherein the insulating layer covers the oxidesemiconductor and the low conductive region, a carrier concentration ofthe low conductive region is lower than a carrier concentration of thesource region or the drain region, and the carrier concentration of thelow conductive region is gradually varied in the low conductive region.9. The thin film transistor of claim 8, wherein the edge boundary of theinsulating layer is substantially aligned to a boundary between the lowconductive region and the source region or the drain region.
 10. Thethin film transistor of claim 9, wherein the edge boundary of the gateelectrode is substantially aligned to an edge boundary of the oxidesemiconductor.
 11. The thin film transistor of claim 7, furthercomprising a buffer layer disposed between the light blocking layer andthe oxide semiconductor.
 12. The thin film transistor of claim 11,wherein the buffer layer or the insulating layer includes an insulatingoxide.